Automatic telephone-exchange.



No. 776,524. PATENTED DEC. 6, 1904. F. A. LUNDQUIST. AUTOMATIC TELEPHONE EXCHANGE.

APPLICATION FILED APB. 30.1900.

no MODEL. QBHEBTfl-SHEET 1.

2 6 Fl B6 new.

YYITNESSEs: INVENTOR 4 Y aagfl ATTORNEY.

Mum mwmmuv av mu" r. mums mm, rm cw w w.

No. 776,524. PATENTED DEC. 6, 1904. P. A. LUNDQUIST.

AUTOMATIC TELEPHONE EXCHANGE.

APPLICATION FILED APR. 30.1900.

no MODEL. 9 SHEETS-SHEET z.

FJCLZ.

INVENTOR:

ATTORNEY- wrrncsszg; 15 E e (A H5 No. 776,524. v PATENTED DEC. 6, 1904.

' E. A. LUNDQUIST.

AUTOMATIC TELEPHONE EXCHANGE.

I APPLICATION FILED APB. 30.1900. N0 MODEL. 9 SHEETS-SHEET a.

mvEnrrom wrrwzsszs: 3" (a g r 7? BY W MM H ATTORNEY- No. 776,524. I PATENTED DEC. 6, 1904.

' A. LUNDQUIST.

AUTOMATIC TELEPHONE EXCHANGE.

E I APPLIOATION FILED APR. 30, 1900.

N0 MODEL. 9 SHBETfi-SHEBT 4.

JNVENTOR .Qo-M a. BYGQMMML ATTORNEY.

PATENTED DEC. 6, 1904.

F. A. LUNDQUIST. AUTOMATIC TELEPHONE EXCHANGE.

APPLICATION FILED APR. 30,1900- 9 sums-44mm a.

N0 MODEL.

No. 776,524. v I PATENTED DEC. 6, 1.904. F. A. LUNDQUIST.

AUTOMATIC TELEPHONE EXCHANGE.

APPLIOATION FILED APR. 30.1900.

N0 MODEL. 9 SHEETS-SHEET 7.

INVENTOR.

WI NE$$E$1 v I M QNMW O a f, I M4 63W a BY No. 776,524. PATENTED DEC. 6, 1904. I E F. A. LUNDQUIST.

AUTOMATIC TELEPHONE EXCHANGE.

APPLICATION FILED APE. 30,1900.

NO MODEL. 9 SHEETS-SHEET B.

FIG. l0.

INVENTOR wlr Ncsszs'. v I 1 b QJYW BY CM M ATTORNEY.

No. 776,524. PATENTED DEC. 6, 1904. F. A. LUNDQUIST. AUTOMATIC TELEPHONE EXCHANGE.

APPLICATION FILED APR. 30,1900.

N0 MODEL. I 9 SHEETS-$113171 9k FIGJL WITNESSES: 9 M1 l-NVENTOR'.

G r figiiafii f 63M! ZL I BY .ATTJQR N 4;-

ITE 'Srarns Patented December 6', 1 90a.

FRANK A. LUNDQUIST, OF CHICAGO, ILLINOIS, ASSIGNOR TO M. E.

RICHARDSON, TRUSTEE,

OF STERLING, KANSAS,

AUTOMATIC TELEPHONE-EXCHANGE.

SPECIFICATION forming part of Letters Paten No. 776,524, dated December 6, 1904.

Application filed April 30, 1900. Serial No. 14,824:- (No model.)

To all whom it may concern:

Be it known that I, FRANK A. LUNDQUIS'I, a citizen of the United States of America, and a resident of Chicago, county of Cook, and State of Illinois, have invented certain new and useful Improvements in Automatic Telephone-Exchangeaof which the following is a specification.

My invention relates to automatic telephoneexchanges, and more particularly to the switching mechanisms in the central oflice and the manner in which they are electrically connected to each other.

The objects of my invention are to improve the central-office devices and to improve the manner of making electrical connections to these devices.

In the accompanying drawings, Figure 1 is a front elevation of a switch. Fig. 2 is a rear elevation of the same. Fig. 3 and Fig. 4 are side elevations from opposite directions. Fig. 5 is a section substantially on line 5 5 of Figs. 1 and 2. Fig. 6 is a section on line 6 6 of Figs. 1 and 2. Fig. 7 is a detail in plan, partly in section, of some of the parts illustrated in Fig. 1. Fig. 8 is a diagram showing the electrical connections when an auxiliary switch is used in connection between two main switches. Figs. 9 and 10 and 11 taken together are a general diagram showing the groups of main switches and auxiliary switches with three instead of ten taken as a basis. Fig. 12 is an abridged diagram, showing the talking-circuit between two telephonesso as to illustrate the complete metallic connection from one to the other Without going through any common return used by other telephones. Fig. 12 also shows a device whereby cross-talk by induction is prevented in the talking-circuit, and Fig. 13 is a perspective detail.

In the said drawings, represents a vertical frame on which there are the shelves or brackets 21, 22, and 23. Mounted on these brackets is a shaft 28, on which there is a ratchet-wheel 2A and a cylindrical ratchet-rack 25. There are also on shaft 28 two gears 26, which mesh into racks 27, which racks are supported on rods 29, guided in slots in brackets 22 and 23. Secured to the racks 27 is a carriage frame or plate 30, to which are insulatingly connected contact-makers 66 and 92.

On the frame 20, back of the shaft 28 and in the path over which the carriage 30'nioves, is an insulating-block l9, having two groups of rectangularlyarranged contact-points 48 and A7. These are so arranged that when the carriage 30 is moved the contact-maker 92 is moved over the contact-points 48 and the contact-maker 66 is COI'I'GSPODCllHgly moved over the contact-points 4:7.

Secured to the back of the frame 20 is a magnetA, having an armaturelever A on the end of which is a pawl A, adapted to engage the cylindrical ratchet to move the shaft 28 upward, and consequently to carry upward the carriage and all the parts connected thereto. The pawl A has a wire A* projecting from its side in a position to engage another wire A, which is supported in thebrackct 22.

The parts A" and A are so arranged that when the magnet A is not energized they will keep the pawl A out of engagement with the cylindrical ratchet 25. Also secured on the back of the frame 20 is a magnet B, on the armature-lever B of which there is a pawl B", adapted to engage the ratchet-wheel 24 for the purpose of turning the shaft 28, and consequently the gears 26, so as to move laterally the carriage 30. ires B and B" keep the pawl B out of engagement with the ratchetwheel 24: when the magnet Bis not energized. Another wire B serves as a stop for armaturelever B in one direction, and a block B on the frame 20 serves as a stop in the other direction.

Supported on the bracket 22, near the cylinder-rack 25, is a post E, in which is pivoted a holdingpawl E, adapted to engage the ratchet 25 and prevent the downward movement of the shaft 28 until the said pawl has been released, as will be hereinafter described.

On the top of the frame 20 is a magnet C, which has an armature-lever C The lower end of (J is near the lower end of the magnet C and is provided with a hook C, which is adapted to engage a similar hook or catch on a lever J, that is fitted in a post J on top of the frame. The forward end of J projects underneath a collar secured on the upper end of the shaft 28. Then the shaft 28 is at its lowest position, this collar engages the lever J, so as to raise its rear end clear of the hook on the armature-lever Vhen, however, the shaft 28 has been moved upward one step or more, the rear end of the lever J descends, so that if the magnet C be energized the hook will engage the lever J and hold the armature-lever C in its attracted position. Insulatingly secured to the armature-lever C is a metal strip 51, which projects downward and is normally in contact with another metal strip 52. When, however, the magnet C is energized, the movement of the armature-lever 0 moves 51 into contact with the other metal strip 86. When the hook C is engaged and held by lever J, the metal strip 51 is held away from strip 52 and into engagement with the strip 86. As this holding of 51 in contact with 86 can only occur when the shaft 28 has been moved upward from its lowest position, it will be evident that if the shaft be permitted to drop to its lowest position the contact between the collar on the upper end of said shaft and the lever J will release the hook C and permit 51 to again move into connection. with 52. Also on the upper portion of the frame is a magnet D, having an armature-lever D similarly provided with a strip 59, which is moved into contact with a metal contact-point 114: when magnet is energized. Pivoted at F on the frame 20 is a lever F, in the lower end of which is pivoted a second lever F that projects forward into the path of the armature-lever A and also into that of a lateral projection E on the pawl E. The lever F is normally held to the right by a spring wound around the postF and shown in Fig. 7 as having its end extending over the face of said lever. Also pivoted to the lever F is another lever F, the end of which has a hook adjacent to the armature-lever B (See Fig. 7.) From lever F a rod D projects upward and is connected to the armature-lever D so that when the magnet D is energized the lever F is moved with its hook in front of the armature-lever B If while in this position the magnet B be energized, the movement of the armature-lever B will move the lever F to the left, so that a notch in the lever F will engage the projection E on the pawl E. If after this action the magnet B be deenergized, the return movement of the lever F toward the right will draw the pawl E out of engagement with the ratchet 25, so as to permit the shaft 28 to drop by gravity to its lower position. As will be seen by inspection of Fig. 7 the same result will be accomplished by energizing magnet A, so as to move the armature-lever A upward instead of energizing the magnet D, because such movement of the armature-lever A would move the hook on lever F in front of the armature-lever B so that movement of B to the left would in the manner described cause F to engage E so as to release the pawl E. It will therefore be apparent that by simultaneous action of magnet B with either magnet A or magnet D the pawl E is released from the ratchet 25, so as to permit the shaft 28 to fall to its lowest position.

Pivoted on the bracket 21 and in a post K is a wide-faced pawl K, adapted to engage the ratchet-wheel 2 L when said wheel has been moved upward one step. In its lowest position, as shown in Figs. 1 and 3, the ratchet-wheel is clear from pawl K and may be moved to its normal position, as will be described.

Pivoted on a lug H at the lower end of the frame 20 is a rod H, to the lower end of which rod is pivoted a link H having its other end pivoted to a step-block H for the shaft 28.

Surrounding the lower end of the shaft 28 and having one end secured to said shaft and the other to the step H is a spring H, the action of which is to return the shaft 28 to its normal position when the ratchet-wheel 24 is released from its pawl K.

Secured on a portion of the armature-lever A are a series of contact-makers 68, 87, and 117, which are adapted to engage, respectively, the contactstrips 63, 88, and 118. The armature-lever A in its normal position is in engagement with another contact-strip 56. The use of these various contact-strips will be more readily understood in the description of the circuits as they are illustrated in Fig. 8 and as they will be hereinafter described.

In operating the switch the magnet A is first operated to move the shaft 28 upward one step. The operation, or rather the movement, of the armature-lever A raises the lever F clear of the projection E on the pawl E, so as to permit the said pawl to drop into engagement with the ratchet 25 and hold the shaft 28 in its upward position when the magnet A is released. The upward movement of the shaft 28 brings the ratchet-wheel 24 into line with the pawl K, so that when the magnet B is energized to turn the ratchet 24; the said pawl will prevent backward movement. The ratchet 24 may be turned any required number of steps after the shaft 28 has been moved upward one step and before it has been moved upward a second step. WVhen, however, the shaft 28 has been moved upward two steps, the ratchet 24 passes out of the path of the pawl B so that further operation of the magnet B does not afiect the shaft 28. Assuming that by the successive operations of magnets A and B the shaft 28 has been moved upward several steps and also has been rotated several steps, then by the successive and simultaneous operation of the magnets A and B or magnets D and B the hook on the lever F will be pushed upward by magnet A or magnet D into the path of the armaturelever B so thritby the action of the magnet B the lever F will hook upon the projection F on the pawl E. Then upon the release or breaking of the circuits through the two 0perated magnets the lever F, and consequently the lever F, will be moved to the right, as shown in Fig. 7, drawing the pawl F/ out of engagement with the ratchet 25. The shaft 28 will then fall by gravity to its lowest position, at which lowest position the ratchetwheel 24 passes out of engagement with the pawl K, which permits the spring H to return the shaft to its normal position, which normal position is determined by a pin H on the shaft 28 coming in contact with a post H on the lower part of the switch. It will be observed that in this construction and arrangement the return movement of the shaftto its lowest position and also to its rotative position does not occur until after the electric circuits are broken through the two operated magnets. While it would be immaterial mechanically whether the return occured before or after the breaking of the circuits through the magnets, it does make a difference in this case, because in the grouping of electric switches, as will be hereinafter described, if the return should take place before the circuits are broken such return would of itself break some other circuits before the operation is completed.

In arranging an electrical exchange I used one switch like that described for each telephone of the exchange. Assuming that the number of contact-points in one of the groups 47 or 48 is equal to one hundred, then the capacity of the switch would befor one hundred telephones in the exchange, provided that there are direct connections from one switch to the other. In the present drawings, however, Ihave illustrated main switches and auxiliary switches. The main switch is made according to the drawings illustrated and has contact-points thereon, as will appear in the description of the circuits. The auxiliary switches are substantially the same, except that the magnets G and D are omitted and a magnet G, as shown in Fig. 8, is arranged for the purpose of making certain electrical connections on the auxiliary switch. There is also a slight difference in the electrical connections to a main switch and to an auxiliary switch. Assuming one hundred contact-points on each group of contact-points on the main switch and auxiliary switches and arranged as shown in the diagrams, these switches may be used to a capacity of one thousand telephones in the exchange. The difference between direct connections between the switch belonging to one telephone and similar switches belonging to other telephones and connections through auxiliary switches in the manner shown may be illustrated as follows: With a switch having one hundred contactpoints in one group in direct connection the capacity will be for one hundred telephones. If, however, I use the same switches in ten groups of one hundred in each group. then supply ten auxiliary switches for each group, I have one thousand andone hundred switches, each of which has one hundred contact-points in one of its groups. If I made the same switches for one thousand capacity by direct connection, I should have to have one thousand contact-points in each group. There would therefore be for direct connection one thousand multiplied by one thousand, equal to one million contact-points on the switches to accomplish this result; By the grouping method, however, using auxiliary switches, I have one thousand one hundred switches with one hundred contact-points each. which will give a total number of contact-points of one hundred and ten thousand as against one million contact-points.

In carrying out an exchange involving auxiliary switches I arrange the central oh'ice as illustrated in 9, l0, and 11, in which there is a main switch for each telephone in the exchange and a group of ten auxiliary switches for each one hundred of said main switches. The diagram, however, shows the grouping abridged in number, but on 'the same general plan. This abridgment takes three instead of ten as the basis. Hence a group of main switches takes three times three or nine main switches, and the corresponding group of auxiliary switches is three in number. The diagram shows one group of main switches and part of'a second group. It also shows the first and second groups of auxiliary switches and a numbered series, of telephones corresponding to the main switches. There is a bank of wires 106 and 111, arranged in pairs, which serve as connections between the branches 105 and 112 (which run to contact-points on the auxiliary switches) and the branches 107, and 110, which connect to the normal contact-points on the main switches. A second bank of wires 69 and 94:, also arranged in pairs, serve as connections between the branches 67 and 98 (which ran to contact-points on the main switches) and branches 71 and 78, which run to the contactmakers 72 and 10 on the auxiliary switches. There extends from one pole of thebattery X a wire 100, which is provided with branches running to the operating-magnets on the main and auxiliary switches. The wire 101 extends from the other pole of thebattery X and has branches extending to the telephones No. 1, N o. 2, &c. From each telephone there extend the wires 50 and 55 through several intermediaries to the contact-makers 66 and 92 on the corresponding main switches. The intermediaries between the telephones and their. contact-makers are omitted in the general diagram, but are shown in detail in Fig. 8. Referring to Fig. 8 and assuming that a subscriber at the telephone V (shown at the left hand of the drawing) wishes to talk to some other scriber closes a contact marked 1st at his telephone, which sends an electrical impulse through the magnet A of his switch. The operation of A moves the shaft 28 one step and closes the connection between said shaft, which is in electrical connection with the base of the switch to an insulated contact represented by a post 58 in Fig. 8 and by a metallic strip 58 in Fig. 1. He then closes another contact marked 2nd at his telephone, which sends an electrical impulse through the connection which is made and through the magnet B, which rotates the shaft 28 to move his contactmakers 66 and 92 laterally. He repeats this electric circuit through the magnet B as many times as is required to bring the contact-makers opposite the required vertical rows of contact-points. He then makes ten successive electrical connections through the magnet A, precisely as in the first place, moving the contactmakers upward on their respective rows. As soon as these contact-makers reach the contact-points which are in electrical connection with an unemployed auxiliary switch there are set up two other electric circuits, one of which automatically stops his own switch opposite these connections, so that the contacts he is making at his telephone no longer move the contact-makers upward. The second electrical circuit passes through the unemployed auxiliary switch which is thus selected and automatically moves it to a position so that another switch cannot reach it. He then follows by a series of contacts made in his telephone to energize magnets A and B of the selected auxiliary switch, so as to move it into electrical connection with the required main switch. He is then in a position to talk to the called subscriber. When through talking, he makes simultaneous electric circuits through both lines from his telephone, one of which passes through the magnet D on his main switch and the magnet A on his auxiliary switch and the other of which passes through the magnets B B on the switches. For eonvenience of reference I have marked the magnets A and B of the auxiliary switch as magnets A and B, respectively, so as to distinguish their location from those of the main switch.

Before describing the circuits in detail I will refer more particularly to the system of grouping involving auxiliary switches which I have illustrated. l have spoken of the contact-points on a switch as being divided into two groups of one hundred each. These two groups may more particularly be referred to as pairs of groups and a reference to one group will equally represent a reference to the other group. Assuming for the moment that hundred contact-points, as illustrated in Fig.

1, this is divided into ten subgroups or vertical rows of contact points each row of which represents a group of auxiliary switches in the exchange. For example, the first row of ten contact-points represents the first group of ten auxiliary switches, which in turn are used to make connection to the first group of one hundred main switches. In like manner the second subgroup or vertical row of contact-points represents the second group of auxiliary switches, which are usedto make connection with the second group of one hundred main switches. The electrical connections are so made that any one auxiliary switch of the first group may be used to make electrical connections with any one of the one hundred switches in the first group of main switches. In like manner any one auxiliary switch of the second group can be used to make connection to any one of the main switches of the second group. The subscriber thereforeselects the group that he wishes by moving his contactmaker laterally to the proper row, as has been described. He then advances his contact-maker on this row, and the electrical connections are so made that the first idle auxiliary switch is automatically selected and isolated for his use, while at the same time his switch is automatically stopped in connection with that auxiliary switch. If another subscriber wishes to call some person in the same group, he cannot connect his main switch to this auxiliary switch until after the person who is using it has released it and permitted it to return to its normal position. The manner in which these electrical connections are made is illustrated in Figs. 9, 10, and 11 much better than they can beset forth in words.

Returning now to the circuits previously mentioned and describing them in detail, reference being bad to Fig. 8, they will be as follows: The subscriber who wishes to call another closes a contact which we may call the first contact at his telephone, when a current flows as follows: X, 101, Tel. V, 50, 51, 52, 53, A, 54, 100, X. This energizes the magnet A and moves the shaft 28 upward one step, so as to bring the contact-point 57- into electrical connection with the contact-point 58. The contact-point 57 is in electrical connection with the base of the switch, so that any current which passes to the mechanism of the switch passes also to the contact-maker 57. The movement of the switch also moves the contact-makers 66 and 92 away from their normal position,so that another switch cannot connect to the one which has commenced to call. He then closes another contact at his telephone, which we will call the second contact, when a current flows as follows: from battery X, 101, Tel. V, 55, 56, A 28, 57, 58, 59, 60, B, 61, X. This rotates the shaft 28 and moves the contact-makers 66 and 92 laterally one step into line with the next row or subgroup of contact-points on his switch. He repeats this operation until his contact-makers have reached the position to connect with the required group. He then repeats the previous operation of closing the first contact ten successive times, sending a series of impulses again through the magnet A to move the shaft 28 upward, and consequently the contactmakcrs 66 and 92 upward on the respective rows of contact-points to which they were previously moved. In moving upward when the contact-makers reach a contact-point on the rows or subgroups which represent and are connected to an auxiliary switch not in use there is immediately completed through those contactpoints a circuit as follows: from battery Z, 62, 68, 63, G, 64, 65, 66, 67, 69, 70, A of the selected auxiliary switch 71, 72,73, Gr, 74:, Z. This operates the magnet G so as to move its armature-lever Gr to connection with the contact 76, when a second circuit flows from battery X, 101, 75, G, 76, 77, 78, 79, A, 80, 100, X. This operates the magnet A of the auxiliary switch, which is equivalent to the magnet A of the'main switch, and consequently moves its shaft and the corresponding contact-makers upward one step. To avoid confusion the contact-makers of the auxiliary switch are given numbers different from those given for the contact-makers of the main switch, though they are, in fact, iden tical. The movement of the contact-makers breaks the connection 72 73 to the magnets G; but the movement of the armature-lever (it closes this connection through a branch line between 83 and 84:, so that the circuit through G is not actually broken until it is broken at the telephone. This branch circuit goes from through G by way of 81, 82, 83, 8 1, 85, 73, Gr, &c. This acts as a safety for the magnet G. The operation of themagnet C after A has been operated, so as to raise the collar on the upper end of the shaft 28 away from the lever J, permits J to catch the armature-lever G so as to hold 51 away from 52 and into engagement with 86. For the sake of condensation the armature-lever G and the contact-strip 51 are shown in Fig. 8 as being one and the same piece and marked 51. This operation of the magnetG breaks the circuit of the magnet A, so that it cannot be operated another time from the telephone. To prevent this breaking of the circuit through the magnet A from being so quickly made as to interfere with the operation of the parts there is a safety consisting of a short circuit for the magnet A, made by the connection or contact produced by 87 connecting to 88, thus holding the circuit complete to the magnet A until it is broken at the telephone. When the connection is broken at the telephone, the line or circuit through the magnet A is opened in all directions, and the magnet A cannot then be operated until some further operations have been completed. It will be observed that in the process just described the instant the contact-makers of the calling-switch reach a contact-point on the selected group which represents an auxiliary switch not in use the switch of the calling subscriber is automatically stopped at that connection and the selected auxiliary switch is automaticz'illy moved so as to break the connection by which it is initially moved from any calling subscriber, the consequence of which is that the selected auxiliary switch is isolated for the use of the person who has connected to it. When magnet A moves contact-makers 66 and 92 upward to connect with a busy auxiliary switch, the circuit, which would be closed through magnet C for an idle auxiliary switch, is open between 72 and 73, and contact 51 remains on contact 52, so that the circuit through magnet A is intact and the succeeding impulse carries contact-makers 66 and 92 beyond the busy auxiliary switch. It will be apparent that in making these ten contacts the only object is to make enough, so as to be certain to connect to one of the idle switches, and all contacts more than is necessary to pass the employed switches are blank contacts and have no effect whatever. After having made these ten contacts through the first contact at his telephone he then makes a contact at the second contact at his telephone, when a current flows as follows: X, 101, Tel. V, 55, 56, A290, 1), 91, 92, 93, 9 1, 78, 79, A of the selected auxiliary switch 80, 100, X. This moves the selected auxiliary switch one step farther with the contact maker 72 into contact with the metal strip 95. He follows this by again making contact with his first contact, when a current flows as follows: X, 101, Tel. V, 50, 51, 86, (51 having been moved into connection with 86 by the operation of the magnet C,) 65, 66, 67, 69, 70, A 71, 72, 95, 96, 97, B, 98, 99, 102, 103, 80, 100, X. This moves the contact-makers laterally to successive rows or subgroups of contact-points on the auxiliary switch and is repeated until the required group is reached. When the required group is reached, he closes the second contact at his telephone, when a current flows as follows: X, 101, Tel. V, 55, 56, A 90, D, 91, 92, 93, 9 1, 78, 79, A of the selected auxiliary switch 80, 100, X. He repeats this so as to move the contact-makers upward until they reach connection to the required main switch. The talking-circuit will be as follows: Beginning at the left-hand telephone V of Fig. 8, which is assumed to be the calling-telephone, the circuit will be 55, 56, A, 90, D, 91, 92, 93, 94, 78, 10 1, 105, 106, 107 to the normal contact-point on the called switch 92, 91, D, 90, A 56, 55, called. Tel. V,50, 51, 52, 108, 109, 66, 110, 111, 112 to the auxiliary switch 72, 71, A 70, 69, 67 back to 66 of the switch belonging to the calling telephone 65, 86, 51, 50 to the calling Tel. V. To release his own main switch and the selected auxiliary switch, so that they will both return to their normal positions, he makes a simultaneous closure of both his first and second contact-points at his telephone. From the second contact results a current which flows as follows: X, 101, Tel. V, 55, 56, A 90, D, 91, 92, 93, 94%, 78, 79, A of the selected auxiliary switch 80, 100, X. This operates D of the main switch, closing 59 to 114, and also operates A of the auxiliary switch, closing 115 to 116. Closing 59 to 114 sends a current as follows: X, 101, Tel. V, 50, 87, 113, 114, 59, 60, B, 61, X. Closing 115 to 116 also sends a current as follows: X, 101, Tel. V. 50, 51, 86, 65, 66, 67, 69, 70, 81, 115, 116, 97, B, 98, 102, 103, 80, 100, X. It will be seen from these circuits that in the main switch the magnets D and B have been successively and then simultaneously in operation, the result of which, as has been previously described, is to release the shaft 28 and permit the mechanism to return to its normal position. In the selected auxiliary switch it will be seen that the magnets A and B, which correspond to the magnets A and B of the main switch, have been similarly operated, the result of which is also to permit the mechanism of the auxiliary switch to return to its normal position. In case the calling subscriber has not succeeded in making connection to any auxiliary switch, because all of the auxiliary switches of the group happen to be in use at the time or for any other reason, then his two simultaneous circuits made at his telephone would be confined to his own switch and would be as follows: X, 101, Tel. V, 50, 51, 52, 53, A, 5 1, 100, X; also, X, 101, Tel. V, 55, 56, 117, 118, 120, B, 61, X. This operates the magnets A and B and releases the mechanism, as has been previously described.

In tracing the talking-circuit which has been described it will be observed that it does not at any point pass over the battery-line 100 or 101 nor over any line which is or can be common to any other talking-circuit. It will therefore be evident that the talking-circuit is an isolated and purely metallic one from telephone to telephone. There is, however, a branch to the battery-line from each branch of the talking-circuit between two telephones. This arrangement has been shown in condensed form in Fig. 12. The telephone at the left hand of the figure is assumed to have been the calling-telephone and the one at the right hand to have been the called telephone. From the upper line between the contact-maker 92 on the main switch and contact-maker 10 1 on the auxiliary switch there is a branch 79 passing through the magnet A to the battery-line 100. On the lower line between the called telephone and the contact-maker 66 there is another branch line, 53, going through the magnet A of the main switch to the battery-line 100. The magnets A and A are identical magnets on the main and auxiliary switches, re-

spectively. These magnets have the same electrical resistances, so that there is no tendcncy for any induced current to pass from the battery-line to either branch of the two lines between the two telephones. This will be better understood by remembering that the magnets A and A of all the telephones are similarly connected to the battery-line 100. If all of the magnets A were of less resistance than the magnets A, then when conversations are being carried on between two or more pairs of telephones there would be a tendency for the current through the induction-coils of one pair of telephones to leak through the magnet A of one telephone to the line 100 and along this line to and through the magnet A of some other telephone, thus producing cross-talk. By making the resistances of A and A the same the branches from the two sides of the talking-circuit tocorresponding sides of other talking-circuits will be balanced and the talking-current between one pair of telephones will not tend to induce a current to flow to or from either branch of either talking-circuit.

What 1 claim is- 1. In a switching mechanism for an automatic telephone-exchange, a driving-pawl and a holding-pawl,a shaft provided with a ratchetwheel normally held in a position so as to be out of engagement with said pawls, means for moving said shaft axially so as to bring said ratchet-wheel into line of engagement with both of said pawls, and means whereby further axial movement of said shaft will remove said ratchet-wheel from line with the drivingpawl without disturbing its connection to the holding-pawl.

2. In an automatic telephoneexchange,a series of groups of main switches, each switch of which is individual fora connected telephone, and a group of auxiliary switches for each group of main switches, said auxiliary switches being less in number than the main switches and each auxiliary switch being common for connections from any main switch but common for connections to only the switches of the group to which it belongs, substantially as shown and specified.

3. In a telephone-exchange, a series of main switches divided into groups, asmaller group of auxiliary switches for each group of main switches, each auxiliary switch consisting of a pair of contact-makers and devices for moving them into successive contact with a series of pairs of contact-points, a pair of connections from each main switch of a group to a different pair of contactpoints on each auxiliary switch for that group, and a pair of connecting lines from the pair of contact-makers of each auxiliary switch to a position adjacent to the whole series of main switches, said pairs of connecting lines each being provided with branches connecting to corresponding pairs of contact-points on the main switches.

4:. In an automatic telephone-exchange, a series of main switches each of which is provided with a series of contact-points less in number than the number of such main switches, connections from the contact-points of each main switch, a series of auxiliary switches the number of which is equal to the possible connections extending from the contact-points of one main switch, a division of the main switches into groups, and a division of the auxiliary switches into an equal number of groups.

5. In an automatic telephone-exchange, the combination with a main switch provided with two groups of contact-points, the said groups being subdivided into rows, o'f'a series of auxiliary switches connected to corresponding contact-points in the two groups on said main switch, a pair of contact-makers on the main switch and means for moving them to and over corresponding rows of contact-points in the two groups so as to connect the said contact-makers to one of said auxiliary switches, means for similarly moving the selected auxiliary switch, and means whereby such movement of the main switch and one of said auxiliary switches will serve to connect by a complete metallic circuit said main switch with any one of a series of other main switches the munber of which is greater than the number of connections extending from the first-mentioned main switch.

- 6. In an automatic telephone-exchange, the combination with a series of auxiliary switches divided into groups, each member of a group being movable to electrical connection with any one of a more numerous group of main switches, of a series of such groups of main switches, two groups of contact-points on each main switch, said groups of contact-points being subdivided into'vertical rows, and corresponding contactpoints in corresponding rows being considered as a pair of contactpoints, connections from each pair of contactpoints to correspondingauxiliary switches, a pair of contact-makers on each main switch and means for moving them to positions opposite corresponding rows in the two groups of contact-points on such main switch, separate means for moving the contact-makers on a main switch over the rows of contact-points opposite to which they have been previously moved, and automatic means for stopping the movement of said contact-makers when they make contact with a pair of contact-points connected to an auxiliary switch which is at the time at its normal position.

7. In an automatic telephoneexchange, the combination with a series of like auxiliary switches divided into groups, each member of a group being movable to electrical connection with any member of a more numerous and correspondinggroup of main switches, of a series of such groups of main switches, two groups of contact-points subdivided into rows and located on each main switch, connections from the corresponding contact-points in corresponding rows in the two groups to the different members of one of the groups of auxiliary switches, a pair of contact-makers on each main switch and means for moving them to different rows of contact-points so as to select any desired group of auxiliary switches, means for moving the contact-makers over the selected rows of contact-points and means for automatically stopping such movement so as to select the iirst unemployed auxiliary switch in the group of such switches connected to said rows of contact-points, and means For moving the selected auxiliary switch to electrical connection with any member of the corresponding group of main switches.

8. In an automatic telephone-exchange, the combination with a series of telephones, a main switch for each telephone, and a battery and magnets For operating said switches from their connected telephones, of a series of auxiliary switches less in number than the main switches, conductors extending in pairs from the main switches to the auxiliary switches, and other conductors extending in pairs from the auxiliary switches to the main switches.

9. In a telephone-exchange, a series of main switches divided into groups, a less numerous series of auxiliary switches divided into corresponding groups, on each auxiliary switch a pair of contact-points for each member of the group of main switches to which it belongs, pairs of connections between the pairs of contact-points and the corresponding main switches, a pair of contact-makers on each auxiliary switch adapted to be moved to suecessive contacts with pairs of contact-points, devices for so moving them, means for operating said devices from any main switch in the exchange so as to complete electrical connections from the operating-point to a selected member of the group of main switches to which the operated auxiliary switch belongs, and means for preventing a similar operation of the moved auxiliary switch froma second main switch while the said auxiliary switch is in possession of the first main switch.

10. A series of main switches, a series of pairs of insulated contactpoints on each switch, a series of auxiliary switches less in number than the main switches, a series of pairs of contact points on each auxiliary switch, a pair of wires extending from the first auxiliary switch with branches to the first pair of contact-points on each of the main switches, similar connections from each of the other auxiliary switches to corresponding pairs of contact-points on the main switches, a division of the auxiliary switches into groups, and separate pairs of connections from pairs of contact-points on each member of a group to a pair of normal contact-points on a different main switch whereby the said main switches are divided into groups corresponding to the groups of auxiliary switches.

TIC

11. In a telephone-exchange, the combination with a series of main switches each of which is individual fora connected telephonestation and each of which is provided with pairs of electrical connections less in number than the number of such switches, of a series of auxiliary switches equal in number to the number of pairs of electrical connections on one main switch, and means whereby a movement of one main switch and one auxiliary switch wi l serve to establish telephonic connection between the moved main switch and any one of the other main switches in the exchange.

12. In a telephone-exchange, the combination with a series of main switches divided into groups. and a less numerous series of auxiliary switches divided into corresponding groups, of electrical connections extending in pairs from each main switch to all of the auxiliary switches in the exchange, return connections extending in pairs from each auxiliary switch to all of the main switches in the group corresponding to the group in which the auxiliary switch is located, and means whereby a movement of one main switch and one auxiliary switch will serve to make telephonic connections between the moved main switch and any other main switch in the exchange.

13. In an automatic telephone-exchange, a main switch provided with two groups of contact-points, a division of said groups into parallel rows, corresponding rows in the two groups being considered as pairs of rows and corresponding contact-points in a pair of rows being considered as a pair of contact-points, a pair of contact-makers on said switch and means for moving them to electrical connection with pairs of contact-points, an auxiliary switch connected to each pair of contactpoints, said auxiliary switches being divided into groups corresponding to pairs of rows of contact-points on the main switch, a pair of groups of contact-points on each auxiliary switch, and other main switches connected to pairs of contact points on the auxiliary switches, said main switches being divided into groups corresponding to the groups of auxiliary switches and having as many members in a group as there are pairs of contactpoints on one auxiliary switch.

14. In a telephone-exchange comprising a series of groups of electrically-operated main switches and a corresponding series of lesser groups of electrically operated auxiliary switches, means for operating any main switch so as to cause a preliminary selection of any desired group of auxiliary switches, and automatic means for selecting and isolating an idle auxiliary switch out of the preliminary selected group of auxiliary switches.

15. In a telephone-exchange comprising a series of groups of electrically-operated main switches and a corresponding series of lesser groups of electrically operated auxiliary switches, means for operating any main switch so as to cause a preliminary selection of any desired group of auxiliary switches, further means for operating the main switch so as to cause the automatic selection of an idle auxiliary switch out of the preliminary selected group of auxiliary switches, and means for operating the automatically-selected auxiliary switch so as to select any one of the main switches located in the group of main switches which corresponds to the group of auxiliary switches in which is located the automatically-selected auxiliary switch.

16. A series of groups of main switches, a corresponding series of lesser groups of auxiliary switches, electrically-operated means by which any main switch may be moved to electrical connection with one of the auxiliary switches, and electrically-operated means by which the selected auxiliary switch may be moved to electrical connection with any one of the main switches located in the group of main switches which corresponds to the group of auxiliary switches in which the selected auxiliary switch is located.

17. A series of groups of main switches, a lesser group of auxiliary switches apportioned to each group of main switches, electrical conductors from each main switch to all of the auxiliary switches, and return -conductors from each auxiliary switch of each group to all of the main switches located in the group of main switches to which it is apportioned.

18. A series of groups of main switches, a lesser group of auxiliary switches apportioned to each group of main switches, a group of contact-points on each main switch apportioned to each group of auxiliary switches, each contact-point of a group representing a difi'erent auxiliary switch in the group of auxiliary switches, conductors connecting each contact-point with the auxiliary switch which it represents, other contact-points on the auxiliary switches representing the main switches of the group to which the auxiliary switches are apportioned, and return-conductors connecting each contactpoint on an auxiliary switch with the main switches of the group to which it is apportioned.

19. In an automatic telephone-exchange, a series of main switches, each of which is individual for a connected telephone-station, a telephonestation connected to each main switch, a lesser series of auxiliary switches each of which is common for all stations, a series of contact-points on each main switch, one of which is the normal contact-point, other contact-points on each auxiliary switch, a direct connection from the normal contactpoint on each main switch to a definite and correspondingly-located contact-point on each auxiliary switch, and other direct connections to an auxiliary switch that is in its normal position.

21. The combination with a series of movable main switches, and a series of movable auxiliary switches, of electrically-operated devices for moving a main switch to electrical connection with successive auxiliary switches, and means by which the circuit for the electrically-operated devices will be automatically broken when the moved main switch reaches connection to an auxiliary switch which is in its normal position.

22. In a telephone-exchange, the combination with a series of main switches, and a series of auxiliary switches, each main switch being movable to connection with successive auxiliary switches, of devices by which upon operating a main switch such main switch will be automatically associated in electrical connection with the first auxiliary switch which is at the time in its normal position.

23. In a telephone-exchange provided with a plurality of switches any one of which may be used in establishing a talking-circuit between a calling and a desired one of the other stations of the exchange, means for automatically selecting an idle one of such switches, and means for operating the selected switch for establishing such talking-circuit.

24. The combination with the stations of a telephone-exchange, of a plurality of switches any one of which may be used in establishing a talking-circuit between a calling and a desired one of the other stations, means for antomatically selecting an idle one of such switches, and automatic means for isolating the selected switch.

25. The combination with the stations of a telephone-exchange, of aplurality of switches less in number than the number of stations in the exchange, and electrically-operated means by which an automatically-selected one of said switches may be used in establishing a talking-circuit between diflerent stations.

26. The combination with the stations of a telephone-exchange, of a plurality of switches less in number than the number of stations in the exchange, means for automatically selecting an idle one of said switches, and electrically-operated means for moving the selected switch so as to establish a talking-circuit between two stations.

27. The combination with the stations of a telephone-exchange, an electrically-operated device for each station, and connections from each station to its device, of a series of switching mechanisms less in number than the number of stations, means controlled from any station for moving its electrically-operated device so as to automatically select and make connections to an unemployed one of said switching mechanisms, and means controlled from the same place for moving the selected switching mechanism to connection with the electrically-operated device of any one of a I 

